Answer:
C
Explanation:
We see that the shaded area of the rectangle is a right triangle. This is great for us.
The formula for finding the area of a triangle is (base*height)/2=area. Over here, the base is 18 and the height is 6, so we plug in those numbers and get (18*6)/2=108/2=54. I just went ahead and looked at all the answers knowing the answer but you can tell it isn't A or B because there is addition and you can tell it isn't A or C because it doesn't half it.
Please tell me if you have any questions.